Apparatus for heat shaping piston rings



Patented Dec. 4, 1951 APPARATUS FOR HEAT SHAPING PISTON RINGS Mortimer 0.14)/unsford, Sullivan, Mo., assignor, by mesne assignments, to Ramsey Corporation, a

corporation of Ohio Application November 22, 1949, Serial No. 128,870

v1 Claim. l

My invention has relation to improvements in apparatus or" heat-treating piston rings and it consists in the novel features of construction more fully set forth in the specication and pointed out in the claim.

The principal object of the invention is to heat the piston rings by electrical induction while they are held in proper shape by passage over a suitable form. The form is the essential part of a fixture on which the rings are loaded and continuously advanced past the induction coil to ultimately discharge on to a conveyor passing through a cooling medium.

The present invention is an improvement over that shown in U. S. Patent No. 2,465,897 granted on March 29, 1949 to M. W. Marien and Carl E. Lippmann and is designed to overcome certain objectionable characteristics of the apparatus of said patent. The most objectionable of these defects is the tendency to arcing between the form and the rings passing thereover, and it is essentially the object of my invention to eliminate such arcing. The manner in which this is accomplished, together with other advantages of the invention, will be better apparent from a detailed description thereof in connection with the accompanying drawings, in which:

Figure 1 is a side elevation of my fixture mounted over a suitable cooling tank (shown in section) through which a suitable conveyor passes for continuously carrying the rings away after treatment; Figure 2 is a top plan of the xture over which the rings are passed during heat treatment; Figure 3 is a horizontal crosssection taken on the line 3 3 of Fig. l; Figure 4 is a combined section and side elevation of the form (or mandrel) and the ring guide projecting upwardly therefrom taken on the line 4-4 of Fig. l; Figure 5 is a cross-section similar to Fig. 3 showing how impurities accumulate on the mandrel to form a layer ci insulation between the mandrel and the rings; and Figure 6 is a diagrammatic View of the old type of form showing how a differential of potential is built up between the ring ends causing detrimental arcing through the form during the heat-shaping process.

Referring to the drawings, F represents the fixture as a whole which comprises a loader I, a forming element 2, and a lining bar 3. A lug 5 extends from the forming element 2 and is secured by a plate to a standard 'I' extending upwardly from base 8. The base 8 is secured to a boss 9 on the bottom Ii! of quenching tank T which has a uid inlet pipe II and an overow pipe I2 to maintain a constant level of water or other quenching medium. An endless conveyor C is carried by pulleys p, mounted on the tank so that the conveyor will travel beneath the forming element 2 and receive the rings as they discharge therefrom and carry them through the cooling medium to be ultimately discharged from the conveyor in any well-known manner.

In the method of employing the xture F, the rings R are passed over the form or mandrel 2 and subjected to the heat of an induction coil E which surrounds the forming element 2 in suinciently spaced relation to permit the free passage of the rings over the element 2 and within the coil E. The induction coil E is connected to a source of electrical energy represented by line Wires w, w. The forming element 2 comprises a lower cylindrical portion a, and an upper frustroconical section b, upon the latter of which is disposed, and which we choose to term, a loader I held in place thereon by a center pin I3 disposed in a socket I4 in the forming element.

The loader I is provided with a slot Il and the liner bar 3 is secured in slot Il by screws I8. The bar 3 has a rib 2i] extending outwardly from it and tapered from the top to the bottom of the bar. The purpose of this tapering construction is to facilitate the disposition of the rings on loader I with their gaps embracing the liner bar. As the rings pass over the conical portion b of the mandrel 2 they gradually increase in width until the rings enter upon the cylindrical part a of the mandrel at which time the gaps will have been expanded to their normal dimension and the rings will have been properly shaped for the heat treatment about to follow.

The forming element 2 has an axial bore 2l passing entirely through it, and in the upper end is lodged the pin I3, insulated from the element 2 by suitable insulation I5. The element or mandrel 2 has a longitudinally disposed slot or gap 22 extending throughout its length and in alinement with lining bar 3 so that as the rings pass over the form or mandrel 2 their gaps g will be in line with said slot 22. Preferably this slot 22 is filled with heat resisting insulation 23, such as mica. The advantage of the insulating slot 22 may be best understood by referring to Fig. 6 which shows the old construction of Patent No. 2,465,897.

In this construction the mandrel 25 is solid, and as impurities accumulate and build up on the surface of the mandrel they form an effective insulation indicated by 26. There can thus be no free now of current from the mandrel 2 to the rings R. A difference of potential thus builds up between the two ring ends and it will be spent by arcing at the ring ends and between the ring and mandrel as indicated by the double arrow :c (Fig. 6). This arcing damages the ring at the ends and causes pitting of the mandrel surface. By placing the insulating gap 22 in mandrel 2 this arcing is overcome.

In both the old construction (Fig. 6) and the new construction (Figs. 3 and 5) there is no arcing when the surface of the cylindrical part a of mandrel 2 is clean. However, when particles of foreign matter (such as scale, dust, etc.) accumulate on the mandrel surface Aan insulation such as 26 (Fig. 6) and 2l (Fig. 5) forms. This insulation evidently is caused by both the impurities and air spaces resulting therefrom. This separation causes a zero potential in the solid mandrel 25 and a positive potential between the ring ends with no flow of current; exceptby arc,-`

ing from one ring end to the other through the I mandrel.

In the construction of Figures 3 and 5 the insulation Zi-is not? detrimental as an'equal potential will build up in both the mandrel 2 and the rings thereon since both furnish a path for electric current. These potentials, however, are of the same polarity and thus repel each other so no arcing results.

The forming element 2 may be of any desired shapethat ultimately is to be imparted to the piston rings. Of course, the shape generally sought is that which will give the rings uniform radial tension in action. Heretofore, this shape has generally been accomplished by making individual ring castings.

It will be observed that the forming element 2 is of metallic construction and will, therefore, store up heat from the induction coil E. Therefore, as the rings pass over the element 2 they will be exposed to both the heat of the coil on the outside and the heat of the element on the inside. The heating of the rings while under tension on the forming element and also under a limited lateral restraint will set them in their final shape in a matter of seconds.

If desired the mandrel 2 may be chromium plated to increase its wearing properties.

Having described my invention, I claim:

Y A xture for heat-shaping split piston rings comprising a loader, a mandrel in line therewith, a lining bar projecting from the loader for alining the gaps of the rings, an induction coil contiguous to the mandrel, said mandrel having a central bore and a radial slot extending from the bore to its outer surface, said slot being in alinement with the aforesaid lining bar, and'means for moving the rings over the mandrel. f MORTIMER C. DUNSFORD.

REFERENCES CITED The following references are of record in Vthe file of this patent:

UNITED STATES PATENTS Marien et al Mar. 29, 1949 

